U.S. patent number 10,684,515 [Application Number 15/765,072] was granted by the patent office on 2020-06-16 for light-modulating cell.
This patent grant is currently assigned to DAI NIPPON PRINTING CO., LTD.. The grantee listed for this patent is DAI NIPPON PRINTING CO., LTD.. Invention is credited to Norio Ishii, Kumiko Kambara, Tomoya Kawashima, Yusuke Nakamura.
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United States Patent |
10,684,515 |
Nakamura , et al. |
June 16, 2020 |
Light-modulating cell
Abstract
A light-modulating cell includes: a pair of polarizing plates (a
first polarizing plate and a second polarizing plate); a pair of
electrodes (a first transparent electrode and a second transparent
electrode) arranged between the pair of polarizing plates (the
first polarizing plate and the second polarizing plate); and a pair
of alignment films (a first alignment film and a second alignment
film) arranged between the pair of electrodes (the first
transparent electrode and the second transparent electrode). A
plurality of spacers, which support at least any one of the pair of
alignment films and are in two-dimensional contact with at least
any one of the pair of alignment films, is provided. At least some
of the plurality of spacers have an inconstant distance to another
spacer positioned at a closest distance.
Inventors: |
Nakamura; Yusuke (Tokyo,
JP), Kawashima; Tomoya (Tokyo, JP),
Kambara; Kumiko (Tokyo, JP), Ishii; Norio (Tokyo,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
DAI NIPPON PRINTING CO., LTD. |
Tokyo |
N/A |
JP |
|
|
Assignee: |
DAI NIPPON PRINTING CO., LTD.
(Tokyo, JP)
|
Family
ID: |
58423936 |
Appl.
No.: |
15/765,072 |
Filed: |
September 29, 2016 |
PCT
Filed: |
September 29, 2016 |
PCT No.: |
PCT/JP2016/078895 |
371(c)(1),(2),(4) Date: |
March 30, 2018 |
PCT
Pub. No.: |
WO2017/057619 |
PCT
Pub. Date: |
April 06, 2017 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
|
US 20180284514 A1 |
Oct 4, 2018 |
|
Foreign Application Priority Data
|
|
|
|
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Sep 30, 2015 [JP] |
|
|
2015-193538 |
Mar 10, 2016 [JP] |
|
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2016-046985 |
Jul 25, 2016 [JP] |
|
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2016-145616 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E06B
3/66304 (20130101); G02F 1/134309 (20130101); G02F
1/133707 (20130101); G02F 1/13318 (20130101); G02F
1/13392 (20130101); G02F 1/1339 (20130101); G02F
1/13725 (20130101); G02F 1/1337 (20130101); G02F
1/133528 (20130101); G02F 1/13394 (20130101); E06B
3/6722 (20130101); G02F 1/13 (20130101); E06B
2009/2417 (20130101); G02F 2001/13312 (20130101); E06B
2009/2464 (20130101); G02F 2202/043 (20130101); G02F
2001/13398 (20130101) |
Current International
Class: |
G02F
1/1339 (20060101); G02F 1/137 (20060101); G02F
1/1335 (20060101); G02F 1/1343 (20060101); G02F
1/133 (20060101); E06B 3/67 (20060101); E06B
3/663 (20060101); G02F 1/1337 (20060101); G02F
1/13 (20060101); E06B 9/24 (20060101) |
Field of
Search: |
;349/155-158 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
H03-047392 |
|
Feb 1991 |
|
JP |
|
H06-160823 |
|
Jun 1994 |
|
JP |
|
H08-184273 |
|
Jul 1996 |
|
JP |
|
2001-215517 |
|
Aug 2001 |
|
JP |
|
2001-264807 |
|
Sep 2001 |
|
JP |
|
2004-325525 |
|
Nov 2004 |
|
JP |
|
2007-515661 |
|
Jun 2007 |
|
JP |
|
2010-032848 |
|
Feb 2010 |
|
JP |
|
2012-163771 |
|
Aug 2012 |
|
JP |
|
2012-194257 |
|
Oct 2012 |
|
JP |
|
2012-234142 |
|
Nov 2012 |
|
JP |
|
2013-118503 |
|
Jun 2013 |
|
JP |
|
10-2001-0090500 |
|
Oct 2001 |
|
KR |
|
508628 |
|
Nov 2002 |
|
TW |
|
200520990 |
|
Jul 2005 |
|
TW |
|
201300841 |
|
Jan 2013 |
|
TW |
|
Other References
Apr. 3, 2018 International Preliminary Report on Patentability
issued in Patent Application No. PCT/JP2016/078895. cited by
applicant .
Dec. 6, 2016 International Search Report issued in Patent
Application No. PCT/JP2016/078895. cited by applicant .
Mar. 1, 2019 Third Party Observation issued in European Patent
Application No. 16851790.2. cited by applicant .
Apr. 15, 2019 European Search Report issued in European Patent
Application No. 16851790.2. cited by applicant .
Mar. 22, 2019 Information Offer Form issued in Japanese Patent
Application No. 2016-132821. cited by applicant .
Nov. 22, 2019 Office Action issued in Japanese Patent Application
No. 2016-132821. cited by applicant .
Jul. 22, 2019 Office Action issued in Taiwanese Patent Application
No. 105131736. cited by applicant .
Jul. 9, 2019 Office Action issued in Japanese Patent Application
No. 2016-145616. cited by applicant .
Apr. 24, 2020 Office Action issued in Japanese Patent Application
No. 2016-132821. cited by applicant .
Apr. 24, 2020 Office Action issued in Japanese Patent Application
No. 2016-145616. cited by applicant.
|
Primary Examiner: Chang; Charles S
Attorney, Agent or Firm: Oliff PLC
Claims
The invention claimed is:
1. A light-modulating cell comprising: a pair of film substrates; a
pair of electrodes arranged between the pair of film substrates; a
pair of alignment films arranged between the pair of electrodes; a
plurality of spacers supporting at least any one of the pair of
alignment films and being in two-dimensional contact with at least
any one of the pair of alignment films; and a liquid crystal layer
arranged between the plurality of spacers between the pair of
alignment films, wherein the liquid crystal layer contains at least
a dichroic pigment, at least some of the plurality of spacers have
an inconstant distance to another spacer positioned at a closest
distance, at least any one of the pair of film substrates is
partially or entirely curved, no polarizing plate is provided, and
alignment of the dichroic pigment is twisted by 180 degrees or more
with respect to a horizontal direction in a state where no electric
field is applied.
2. The light-modulating cell according to claim 1, wherein each of
the plurality of spacers includes: a first bottom portion which has
a flat shape and is in contact with one of the pair of alignment
films; and a second bottom portion opposing the first bottom
portion.
3. The light-modulating cell according to claim 1, wherein the
plurality of spacers are made of a photocurable resin.
4. The light-modulating cell according to claim 1, wherein the
plurality of spacers are configured by repeatedly arranging unit
patterns each of which is formed of three or more spacers arranged
with a predetermined relative positional relationship.
5. The light-modulating cell according to claim 1, wherein each of
the plurality of spacers has a tapered shape that tapers from one
of the pair of alignment films toward the other alignment film.
6. The light-modulating cell according to claim 1, wherein a taper
angle of each of the plurality of spacers is in a range of
75.degree. or larger and 85.degree. or smaller.
7. The light-modulating cell according to claim 1, wherein each of
the plurality of spacers includes a core portion and a covering
portion covering at least a part of the core portion, each of the
plurality of spacers penetrates through one of the pair of
alignment films and the liquid crystal layer, and each of the
plurality of spacers includes: a first support surface being in
two-dimensional contact with the other alignment film of the pair
of alignment films; and a second support surface being in
two-dimensional contact with one of the pair of electrodes, and the
first support surface is formed by the covering portion, and at
least a part of the second support surface is formed by the core
portion.
Description
TECHNICAL FIELD
The present invention relates to a light-modulating cell that
controls liquid crystal orientation to perform light
modulation.
BACKGROUND ART
For example, an electronic blind or the like in which a
light-modulating cell (light-modulating material) is installed in a
window, a door, or the like, and the transmission of extraneous
light is controlled by the light-modulating cell has been known. It
is possible to suitably employ a liquid crystal, for example, as
such a light-modulating cell.
The light-modulating cell employing the liquid crystal is produced
by, for example, sandwiching a liquid crystal layer between a pair
of transparent film members forming transparent electrodes or
between a pair of alignment films so as to prepare a liquid crystal
cell, and sandwiching this liquid crystal cell between linear
polarizing plates to take linearly polarized light. When
light-modulating is performed by using a light-modulating cell
employing a liquid crystal, the transmission of light is controlled
by controlling an electric field to be applied to the liquid
crystal layer to change orientation of liquid crystal molecules
contained in the liquid crystal layer, and the light-modulating
cell can switch the shielding and transmission of extraneous light
and continuously change the amount of transmitted light, for
example.
For example, Patent Literature 1 discloses a liquid crystal panel
that is provided in a window or a door of a house and capable of
controlling a transparent state and an opaque state. According to
this liquid crystal panel, a plurality of divided liquid crystal
panels are juxtaposed, and each of the divided liquid crystal
panels can be individually controlled between the transparent state
and the opaque state.
In addition, Patent Literature 2 discloses a light control glass
window capable of adjusting light transmittance in various patterns
in accordance with a change of a sunlight situation. According to
this light control glass window, the light transmittance can be
adjusted by changing a voltage acting on a liquid crystal sealed
between two transparent glass plates to change optical
characteristics of the liquid crystal.
CITATION LIST
Patent Literature
Patent Literature 1: Japanese patent application publication No.
03-47392 Patent Literature 2: Japanese patent application
publication No. 08-184273
SUMMARY OF INVENTION
Technical Problem
In a light-modulating cell having a liquid crystal cell, there is a
case where a spacer is provided between the pair of transparent
film members (alignment films) forming the liquid crystal cell, and
the liquid crystal layer is held at a desired thickness by the
spacer. In this case, it is possible to produce an alignment layer
by, for example, preparing the spacer, and then, creating a thin
film of polyimide or the like and subjecting the thin film to
rubbing, and it is possible to regulate the orientation of a liquid
crystal material with this alignment layer.
Such a spacer can be formed using various methods, and it is
possible to accurately form a large number of spacers, regularly
arranged, at once, for example, based on a photolithography
technique. In general, all the spacers are regularly arranged and a
distance between the spacers is adjusted to be constant in order to
simply and accurately form the multiple spacers.
However, as a result of earnest research, the inventors of the
present application have found that, when the regularity relating
to the arrangement of the spacers is high and the distance between
the spacers is constant, the intervals at which lights diffracted
by the respective spacers interfere with each other and intensify
each other also become regular, so that a point light source may be
recognized as blurred light. That is, when the spacers are
regularly arranged, the interference of the diffracted light
generated by the spacers periodically occurs and the diffracted
beams of light periodically intensify each other, and thus, the
point light source looks larger than the original size so that the
visibility of observation light that has passed through the
light-modulating cell deteriorates.
Therefore, it is desired to propose a new method for reducing
influence of the interference of diffracted light generated by the
spacers in the light-modulating cell provided with the multiple
spacers so as to provide the observation light excellent in
visibility. In particular, there is a request for reduction of the
influence of interference of diffracted light generated by the
spacers in order to provide the observation light excellent in
visibility even in a liquid crystal cell employing a guest-host
liquid crystal, which has attracted attention in recent years.
However, a proposal effective in satisfying such a request has not
been made in the related art literatures (for example, the
above-described Patent Literatures 1 and 2).
The present invention has been made in view of the above-described
circumstances, and an object of the present invention is to provide
a light-modulating cell that is capable of reducing influence of
interference of diffracted light generated by a plurality of
spacers and providing observation light excellent in
visibility.
Another object of the present invention is to provide a
light-modulating cell employing a guest-host liquid crystal that is
capable of reducing influence of interference of diffracted light
generated by a plurality of spacers and providing observation light
excellent in visibility.
Solution to Problem
One aspect of the present invention is directed to a
light-modulating cell comprising: a pair of polarizing plates; a
pair of film substrates arranged between the pair of polarizing
plates; a pair of electrodes arranged between the pair of
polarizing plates; a pair of alignment films arranged between the
pair of electrodes; a plurality of spacers supporting at least any
one of the pair of alignment films and being in two-dimensional
contact with at least any one of the pair of alignment films; and a
liquid crystal layer arranged between the plurality of spacers
between the pair of alignment films, wherein at least some of the
plurality of spacers have an inconstant distance to another spacer
positioned at a closest distance.
According to this aspect, the distance between the spacers is
inconstant, and therefore it is possible to reduce the influence of
interference of diffracted light generated by the plurality of
spacers and to provide the observation light excellent in
visibility.
Another aspect of the present invention is directed to a
light-modulating cell comprising: a pair of film substrates; a pair
of electrodes arranged between the pair of film substrates; a pair
of alignment films arranged between the pair of electrodes; a
plurality of spacers supporting at least any one of the pair of
alignment films and being in two-dimensional contact with at least
any one of the pair of alignment films; and a liquid crystal layer
arranged between the plurality of spacers between the pair of
alignment films, wherein the liquid crystal layer contains at least
a dichroic pigment, and at least some of the plurality of spacers
have an inconstant distance to another spacer positioned at a
closest distance.
The light-modulating cell may further include a polarizing plate
provided on the opposite side of the pair of electrodes with one of
the pair of film substrates interposed therebetween.
Each of the plurality of spacers may have a flat first bottom
portion in contact with one of the pair of alignment films and a
second bottom portion opposing the first bottom portion.
According to this aspect, the alignment film can be accurately
supported by each spacer. Incidentally, it is possible to suitably
form the plurality of spacers according to this aspect based on,
for example, a photolithography technique.
The plurality of spacers may be made of a photocurable resin.
According to this aspect, it is possible to easily form each spacer
by utilizing the photocuring performance of the photocurable resin.
Incidentally, it is possible to suitably form the plurality of
spacers according to this aspect based on, for example, a
photolithography technique.
The plurality of spacers may be configured by repeatedly arranging
unit patterns each of which is formed of three or more spacers
arranged with a predetermined relative positional relationship.
According to this aspect, it is possible to easily form the
plurality of spacers while reducing the influence of interference
of diffracted light generated by the plurality of spacers.
Each of the plurality of spacers may have a tapered shape that
tapers from one of the pair of alignment films toward the other
alignment film.
According to this aspect, the alignment film can be accurately
supported by the respective spacers.
A taper angle of each of the plurality of spacers may be in a range
of 75.degree. or larger and 85.degree. or smaller.
According to this aspect, an appropriate alignment regulating force
can be imparted to the liquid crystal layer by the alignment film
while accurately supporting the alignment film with the respective
spacers.
At least any one of the pair of polarizing plates may be partially
or entirely curved.
At least any one of the pair of film substrates may be partially or
entirely curved.
According to these aspects, the light-modulating cell can be
applied to a curved structure.
Each of the plurality of spacers may include a core portion and a
covering portion covering at least a part of the core portion,
penetrate through one of the pair of alignment films and the liquid
crystal layer, and have a first support surface being in
two-dimensional contact with the other alignment film of the pair
of alignment films and a second support surface being in
two-dimensional contact with one of the pair of electrodes, and the
first support surface may be formed by the covering portion, and at
least a part of the second support surface may be formed by the
core portion.
According to this aspect, it is possible to accurately form the
respective spacers based on a so-called photolithography
technique.
Advantageous Effects of Invention
According to the present invention, the distance between spacers is
inconstant, and therefore the periodicity in mutual interference of
diffracted light generated by the respective spacers disappears.
Thus, the influence of interference of diffracted light generated
by the plurality of spacers is reduced, and the observation light
excellent in visibility can be created.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a conceptual diagram illustrating an example of a
light-modulating system.
FIG. 2 is a view illustrating an example of a cross section of a
light-modulating cell.
FIG. 3 is a view for describing a taper angle of each spacer.
FIG. 4 is a view for describing influence of interference of
diffracted light in a case where the spacers are regularly
arranged.
FIG. 5 is a view for describing influence of interference of
diffracted light in a case where the spacers are irregularly
(randomly) arranged.
FIG. 6 is a plan view illustrating a concept of an arrangement
example (modified example) of the spacers.
FIGS. 7A and 7B each illustrate an enlarged sectional shape of a
liquid crystal layer and a spacer, FIG. 7A illustrates a spherical
spacer, and FIG. 7B illustrates a columnar (truncated conical)
spacer illustrated in FIG. 2.
FIG. 8 is a view illustrating another example of a cross section of
a light-modulating cell.
FIGS. 9A and 9B are conceptual views for describing an example
(light shielding state) of a light-modulating cell employing a
guest-host liquid crystal, FIG. 9A is a cross-sectional view of the
light-modulating cell, and FIG. 9B is a plan view of a first
polarizing plate in which an absorption axis direction is indicated
by an arrow "A".
FIGS. 10A and 10B are conceptual views for describing the same
light-modulating cell (a light transmitting state) as FIGS. 9A and
9B, FIG. 10A is a cross-sectional view of the light-modulating
cell, and FIG. 10B is a plan view of the first polarizing plate in
which the absorption axis direction is indicated by an arrow
"A".
FIG. 11 is a conceptual view for describing another example (a
light shielding state) of the light-modulating cell employing the
guest-host liquid crystal, and illustrates a cross section of the
light-modulating cell.
FIG. 12 is a conceptual view for describing the same
light-modulating cell (a light transmitting state) as FIG. 11, and
illustrates a cross section of a light-modulating cell 10.
FIG. 13 is a view for describing an example of a method of
determining a mask pattern.
DESCRIPTION OF EMBODIMENTS
Hereinafter, an embodiment of the present invention will be
described with reference to the drawings. In the drawings attached
to the specification of the present application, a scale, a
dimensional ratio, and the like of each element are conveniently
exaggerated and changed from the actual scale, dimensional ratio,
and the like in order to facilitate the illustration and
understanding. In addition, in this specification, the terms
"plate", "sheet", and "film" are not distinguished from each other
based solely on differences in nomenclature. For example, the term
"plate" is a concept that also includes a member which can be
called a sheet or a film. In addition, the terms specifying shapes,
geometric conditions, and extent thereof used in this specification
(for example, terms such as "parallel", "orthogonal", and "same",
values of a length and an angle, and the like) are understood as
terms meaning ranges of extent where substantially the equivalent
or similar functions can be expected without being bound by strict
meaning.
FIG. 1 is a conceptual diagram illustrating an example of a
light-modulating system 5.
A light-modulating cell 10 of this example has a layer made of a
liquid crystal material containing liquid crystal molecules as will
be described later, and can switch shielding and transmission of
light and change the transmittance (transmissivity) of light. An
object to which the light-modulating cell 10 is applied is not
particularly limited, and typically, the light-modulating cell 10
can be applied to a window, a door, and the like. In particular, a
columnar spacer to be described later is excellent in position
fixing performance, and a position thereof is hardly varied by an
external force such as vibration. Therefore, the light-modulating
cell 10 having the columnar spacer to be described later can be
suitably used even under environment where the external force such
as vibration is applied, and can also be applied to a window (for
example, a skylight) installed in a house.
The light-modulating cell 10 is connected to a light-modulating
controller 12, and a sensor device 14 and a user operation unit 16
are connected to the light-modulating controller 12. The
light-modulating controller 12 controls a light-modulating state of
the light-modulating cell 10 and can switch the shielding and
transmission of light using the light-modulating cell 10 and change
the light transmittance in the light-modulating cell 10.
Specifically, the light-modulating controller 12 can switch the
shielding and transmission of light using the light-modulating cell
10 and change the light transmittance by adjusting an electric
field to be applied to a liquid crystal layer of the
light-modulating cell 10 to change orientation of the liquid
crystal molecules in the liquid crystal layer.
The light-modulating controller 12 can adjust the electric field to
be applied to the liquid crystal layer based on an arbitrary
method. For example, the light-modulating controller 12 can switch
the shielding and transmission of light using the light-modulating
cell 10 and change the light transmittance by adjusting the
electric field to be applied to the liquid crystal layer in
accordance with a measurement result of the sensor device 14 or an
instruction (command) input by a user via the user operation unit
16. Therefore, the light-modulating controller 12 may automatically
adjust the electric field to be applied to the liquid crystal layer
in accordance with the measurement result of the sensor device 14
or may manually adjust the electric field in accordance with the
instruction of the user input via the user operation unit 16.
Incidentally, an object to be measured by the sensor device 14 is
not particularly limited, and, for example, the brightness of use
environment may be measured, and in this case, the switching of the
shielding and transmission of light using the light-modulating cell
10 and the change of the light transmittance are performed in
accordance with the brightness of use environment. In addition, it
is not always necessary for both the sensor device 14 and the user
operation unit 16 to be connected to the light-modulating
controller 12, and any one of the sensor device 14 and the user
operation unit 16 may be connected to the light-modulating
controller 12.
FIG. 2 is a view illustrating an example of a cross section of the
light-modulating cell 10.
The light-modulating cell 10 of this example includes: a pair of
polarizing plates (a first polarizing plate 21 and a second
polarizing plate 22); a pair of transparent electrodes (a first
transparent electrode 25 and a second transparent electrode 26)
arranged between the pair of polarizing plates; and a pair of
alignment films (a first alignment film 27 and a second alignment
film 28) arranged between the pair of transparent electrodes. In
addition, a pair of film substrates (a first film substrate 23 and
a second film substrate 24) are arranged at each outer side of the
pair of transparent electrodes (the first transparent electrode 25
and the second transparent electrode 26) between the pair of
polarizing plates (the first polarizing plate 21 and the second
polarizing plate 22) in this example. That is, the pair of
transparent electrodes (the first transparent electrode 25 and the
second transparent electrode 26) are arranged between the pair of
film substrates (the first film substrate 23 and the second film
substrate 24), and the pair of polarizing plates (the first
polarizing plate 21 and the second polarizing plate 22) are
arranged at each outer side of the pair of film substrates (the
first film substrate 23 and the second film substrate 24).
Furthermore, a plurality of columnar spacers 30, which support at
least any one of the pair of alignment films (the first alignment
film 27 in this example) and are in two-dimensional contact with,
that is, surface contact with at least any one of the pair of
alignment films (the first alignment film 27 in this example), are
provided in this example. In addition, portions among the plurality
of spacers 30 are filled with liquid crystal layers 29 between the
pair of alignment films (the first alignment film 27 and the second
alignment film 28).
Incidentally, the plurality of spacers 30 preferably extend at
least between a "boundary surface Sb2 between the first alignment
film 27 and the liquid crystal layer 29" and a "boundary surface
Sb1 between the second alignment film 28 and the liquid crystal
layer 29". Therefore, for example, the plurality of spacers 30 may
be arranged only between the first alignment film 27 and the second
alignment film 28. In addition, the plurality of spacers may be
provided so as to penetrate through the second alignment film 28
and the liquid crystal layer 29 from the second transparent
electrode 26 (a "boundary surface Sb3 between the second
transparent electrode 26 and the second alignment film 28" in the
example illustrated in FIG. 2) and be in contact with the first
alignment film 27 as indicated by reference sign "30a" in FIG. 2.
Incidentally, it is possible to apply the present invention in the
same manner in both the case where the spacer 30 is provided only
between the first alignment film 27 and the second alignment film
28 and the case where the spacer indicated by reference sign 30a of
FIG. 2 is provided.
Each of the first polarizing plate 21 and the second polarizing
plate 22 has a unique polarization axis and a unique absorption
axis, and allows only light polarized in a specific direction to
pass therethrough. For example, when light traveling in a direction
from the second polarizing plate 22 to the first polarizing plate
21 (see an arrow "L" in FIG. 2) is incident on the light-modulating
cell 10, only light polarized in the same direction as the
polarization axis of the second polarizing plate 22 out of the
light passes through the second polarizing plate 22 and enters the
second film substrate 24, and further, only light polarized in the
same direction as the polarization axis of the first polarizing
plate 21 out of the light traveling from the first film substrate
23 toward the first polarizing plate 21 passes through the first
polarizing plate 21 and travels toward the outside. An arrangement
form of the first polarizing plate 21 and the second polarizing
plate 22 is not particularly limited, and the arrangement form of
the first polarizing plate 21 and the second polarizing plate 22 is
determined in relation to an alignment state of the liquid crystal
molecules contained in the liquid crystal layer 29.
Representative examples thereof include a state called "cross
nicol" where the first polarizing plate 21 and the second
polarizing plate 22 are arranged so as to have the polarization
axes orthogonal to each other and a state called "parallel nicol"
where the first polarizing plate 21 and the second polarizing plate
22 are arranged so as to have the polarization axes parallel to
each other.
For example, when it is desired to improve the rigidity of the
light-modulating cell 10, the first film substrate 23 and the
second film substrate 24 are configured using a transparent member
having excellent rigidity. In addition, it is easy to perform
"bonding of the light-modulating cell 10 to a curved surface",
which is difficult in the case of using a glass substrate, by using
the first film substrate 23 and second film substrate 24 each of
which has a sufficiently flexible film shape.
The first transparent electrode 25 and the second transparent
electrode 26 apply a desired electric field to the liquid crystal
layer 29 as a voltage is applied thereto by the light-modulating
controller 12 (see FIG. 1). Each member forming the first
transparent electrode 25 or the second transparent electrode 26 and
an arrangement form of the first transparent electrode 25 and the
second transparent electrode 26 are not particularly limited. For
example, the first transparent electrode 25 and the second
transparent electrode 26 can be formed using a member excellent in
visible light transmissivity and conductivity such as indium tin
oxide (ITO).
The first alignment film 27 and the second alignment film 28 are
members configured to align the liquid crystal molecules contained
in the liquid crystal layer 29 in a desired direction. Although a
method of aligning the liquid crystal layer 29 according to the
first alignment film 27 and the second alignment film 28 is not
particularly limited, a twisted nematic (TN) liquid crystal in
which molecular arrangement (molecular orientation) is twisted by
90 degrees is used in this example. Incidentally, a method of
imparting alignment functions of the first alignment film 27 and
the second alignment film 28 is not particularly limited, and, for
example, alignment directions of the first alignment film 27 and
the second alignment film 28 may be defined by rubbing using a
member such as nylon, or the alignment directions of the first
alignment film 27 and the second alignment film 28 may be defined
by irradiation with linearly polarized ultraviolet rays.
Each of the plurality of spacers 30 is in surface contact with at
least any one of the pair of alignment films (the first alignment
film 27 in this example), and has a tapered shape that tapers from
one of the pair of alignment films (the second alignment film 28 in
this example) toward the other alignment film (the first alignment
film 27 in this example). In this example, each of the plurality of
spacers 30 has a flat first bottom portion 31 in contact with one
of a pair of alignment films (the first alignment film 27 in this
example) and a second bottom portion 32 opposing the first bottom
portion 31. Incidentally, a portion of each of the spacers 30 on
the boundary surface Sb1 between the second alignment film 28 and
the liquid crystal layer 29 is illustrated as the second bottom
portion 32 for the sake of convenience in FIG. 2, but a portion of
each of the spacers 30 on the boundary surface Sb3 between the
second alignment film 28 and the second transparent electrode 26
may be regarded as the second bottom portion 32 when each of the
spacers 30 extends from the boundary surface Sb3 between the second
alignment film 28 and the second transparent electrode 26 as
indicated by reference sign "30a".
The spacer 30 illustrated in FIG. 2 has a truncated conical shape
in which a diameter linearly changes in accordance with a distance
from the second alignment film 28 and an angle of a side surface is
substantially constant, but is not limited thereto. The diameter of
the spacer 30 may change nonlinearly in accordance with the
distance from the second alignment film 28, and, for example, the
diameter may change exponentially with respect to the distance from
the second alignment film 28, or the diameter may change in
proportion to a square root of the distance from the second
alignment film 28. In addition, the spacer 30 has the tapered shape
(forward tapered shape) that tapers from the second alignment film
28 toward the first alignment film 27 in the example illustrated in
FIG. 2, but may have a tapered shape (inverted tapered shape) that
tapers from the first alignment film 27 toward the second alignment
film 28.
Incidentally, a taper angle .theta. of each of the plurality of
spacers 30 is preferably in a range of 75.degree. or larger and
85.degree. or smaller from the viewpoint of realizing the desired
orientation of the liquid crystal layer 29 while securing the
function as the spacer.
FIG. 3 is a view for describing the taper angle .theta. of each of
the spacers 30. The taper angle .theta. of each of the spacers 30
referred to herein is represented by an angle formed between a
tangent Lt of a side portion Lp of each of the spacers 30 at a
position, separated from the lowermost position of each of the
spacers 30 by one third (1/3) of a distance between both end
portions of each of the spacers 30 (between the uppermost position
(the first bottom portion 31) and the lowermost position (the
second bottom portion 32) of each of the spacers 30 in FIG. 3) with
respect to a stacking direction in a cross section of each of the
spacers 30, and a line H extending in the horizontal direction
vertical to the stacking direction. That is, the taper angle
.theta. of each of the spacers 30 is represented by the angle
formed between the tangent Lt of the portion Lp of a side surface
of each of the spacers 30, separated from the second bottom portion
32 by the distance corresponding to one third of the entire length
of each of the spacers 30 in the stacking direction, and the line H
extending in the horizontal direction.
In addition, at least some of the plurality of spacers 30 have an
inconstant distance to the other spacer 30 positioned at the
closest distance in the present embodiment. That is, in the example
illustrated in FIG. 2, a "distance (interval) D1 between the center
spacer 30 and the left spacer 30" and a "distance D2 between the
center spacer 30 and the right spacer 30" satisfy a relationship
"D1.noteq.D2".
The distance between the spacers 30 indicating the "distance to the
other spacer 30 positioned at the closest distance" is typically
represented by the closest distance between the spacers 30. For
example, in the case of the spacer 30 having the forward tapered
shape illustrated in FIG. 2 (that is, a size of the first bottom
portion 31<a size of the second bottom portion 32), the
"distance between the spacers 30" is represented by a distance
between the second bottom portions 32. On the other hand, in the
case of the spacer 30 having the inverted tapered shape (that is,
the size of the first bottom portion 31>the size of the second
bottom portion 32), the "distance between the spacers 30" is
represented by a distance between the first bottom portions 31.
FIG. 4 is a view for describing influence of interference of
diffracted light in a case where the spacers 30 are regularly
arranged. Incidentally, FIG. 4 illustrates a case where the
plurality of spacers 30 are two-dimensionally arranged with respect
to two directions, that is, a light traveling direction L and a
direction orthogonal to the traveling direction L, but the similar
influence is exerted even in a case where the spacers 30 are
arranged one-dimensionally in the direction orthogonal to the light
traveling direction L.
When the spacers 30 are regularly arranged and the distance between
the adjacent spacers 30 (in particular, the distance with respect
to the direction orthogonal to the light traveling direction L) is
constant as illustrated in FIG. 4, interference of diffracted light
periodically occurs, and a region of visible light is enlarged.
Thus, when assuming light from a point light source, the diffracted
beams of light intensify each other at a constant period if the
distance between the adjacent spacers 30 is constant, and thus, the
influence of interference of diffracted light increases so that the
light from the point light source looks greatly blurred.
FIG. 5 is a view for describing influence of interference of
diffracted light in a case where the spacers 30 are irregularly
(randomly) arranged. Incidentally, FIG. 5 illustrates a case where
the plurality of spacers 30 are two-dimensionally arranged with
respect to two directions, that is, the light traveling direction L
and the direction orthogonal to the traveling direction L, but the
similar influence is exerted even in a case where the spacers 30
are arranged one-dimensionally in the direction orthogonal to the
light traveling direction L.
When the spacers 30 are irregularly arranged and the distance
between the adjacent spacers 30 (in particular, the distance with
respect to the direction orthogonal to the light traveling
direction L) is inconstant as illustrated in FIG. 5, the
interference of diffracted light does not periodically occur, and
the region of visible light does not change. Thus, when assuming
the light from the point light source, an interference zone of
diffracted light becomes random and the light intensity of extent
where it is difficult to visually recognize the influence of
interference of diffracted light is realized if the distance
between the adjacent spacers 30 is ununiform, and thus, it is
possible to view the light from the point light source with its
original size.
Therefore, it is possible to reduce the influence of interference
of diffracted light generated by the plurality of spacers 30 and to
provide the observation light excellent in visibility by using the
light-modulating cell 10 in which "at least some of the plurality
of spacers 30 have the inconstant distance to the other spacer 30
positioned at the closest distance" according to the present
embodiment.
A method of determining specific positions of "the plurality of
spacers 30 whose distance to the other spacer 30 positioned at the
closest distance is inconstant" is not particularly limited, and
can be appropriately determined based on an arbitrary method. For
example, the specific positions of the plurality of spacers 30 may
be determined following a method of defining a generating point of
the Voronoi diagram. In addition, the specific positions of the
plurality of spacers 30 may be determined by, for example, defining
the maximum value and the minimum value of the distance between the
two spacers 30, adjacent to each other, and using these values as
constraint conditions.
Incidentally, it is unnecessary for all the spacers 30 provided in
the light-modulating cell 10 to satisfy the condition that the
"distance to the other spacer 30 positioned at the closest distance
is inconstant", and it is possible to reduce the influence of
interference of diffracted light and to provide the observation
light excellent in visibility even when only some of the spacers 30
satisfy the condition that the "distance to the other spacer 30
positioned at the closest distance is inconstant".
In addition, all the spacers 30 provided in the light-modulating
cell 10 may be randomly arranged with no mutual relation, but the
plurality of spacers 30 provided in the light-modulating cell 10
may be configured by repeatedly arranging the unit patterns each of
which is formed of a plurality of spacers 30 (three or more spacers
30) arranged with a predetermined relative positional
relationship.
FIG. 6 is a plan view illustrating a concept of an arrangement
example (modified example) of the spacers 30. In the example
illustrated in FIG. 6, a condition that "the distance to the other
spacer 30, positioned at the closest distance, is inconstant" is
satisfied with respect to the plurality of spacers 30 (unit
patterns 34) included in a predetermined unit pattern area 50.
Further, the plurality of spacers 30 provided in the
light-modulating cells 10 are configured by repeatedly arranging
the plurality of spacers 30 (unit patterns 34) included in the unit
pattern area 50. Although a shape and a size of the unit pattern
area 50 are not particularly limited, it is preferable to define a
rectangular area defined depending on the entire area where the
spacers 30 are provided as the unit pattern area 50, and, for
example, it is also possible to define a square area having one
side of 10 mm as the unit pattern area 50. In addition, the
specific number and arrangement of the spacers 30 included in the
unit pattern area 50 are not particularly limited either.
As the plurality of spacers 30 (unit patterns 34) included in the
unit pattern area 50 are repeatedly arranged in this manner, it is
possible to easily provide a large number of the spacers 30 while
effectively reducing the influence of interference of diffracted
light generated by the respective spacers 30. Therefore, this
modified example is suitable, for example, when the area where the
spacers 30 are provided is wide.
Incidentally, the spacer 30 according to the present embodiment has
the columnar shape as described above, and thus, is excellent in
not only a position fixing property, but also an optical alignment
property.
FIGS. 7A and 7B each illustrate an enlarged sectional shape of the
liquid crystal layer 29 and the spacer 30, FIG. 7A illustrates a
spherical spacer 30, and FIG. 7B illustrates the columnar
(truncated conical) spacer 30 illustrated in FIG. 2. In general,
the spacer 30 affects the orientation of the liquid crystal layer
29, and thus, the orientation of the liquid crystal layer 29 tends
to be disturbed in the vicinity of the spacer 30. Therefore,
regions in the vicinity of the spacer 30 indicated by reference
sign "35" in FIGS. 7A and 7B become unstable areas relating to the
orientation of the liquid crystal layer 29, and the light passing
through the unstable area 35 may be polarized in an unintended
direction in some cases. When comparing the spherical spacer 30
(see FIG. 7A) with the columnar spacer 30 (see FIG. 7B), in
general, the columnar spacer 30 has smaller influence (see
reference sign "S" in FIGS. 7A and 7B) on the unstable area 35 than
the spherical spacer 30. That is, the unstable area 35 is defined
depending on a surface shape of the spacer 30, and a "range where
light passes through the unstable area 35 (see reference sign "S"
in FIGS. 7A and 7B)" tends to be larger in the "spherical spacer 30
(having a tangent in the same direction as the light traveling
direction)" than in the columnar spacer 30 having a tapered shape
(not having the tangent in the same direction as the light
traveling direction)".
According to the columnar spacer 30 excellent in the position
fixing property and optical alignment property as described above,
it is possible not only to accurately serve the intrinsic function
of the spacer such as securing a space between the alignment films
(the first alignment film 27 and the second alignment film 28) even
under environment where the external force such as vibration is
applied, but also to accurately control a polarization state of
light passing through the liquid crystal layer 29. Therefore, the
light-modulating cell 10 (the spacer 30 (see FIGS. 7A and 7B))
according to this embodiment described above can be suitably used,
for example, in a window (for example, a skylight of a house) or
the like. In particular, the skylight of the house or the like does
not necessarily have a flat structure in design, and may be
required to have a curved structure. Even in such a case, it is
also possible to curve all or a part of at least one of the pair of
polarizing plates (the first polarizing plate 21 and the second
polarizing plate 22), to curve other members (see reference signs
"23" to "30" in FIG. 2), and to curve the entire light-modulating
cell 10 according to the light-modulating cell 10 (spacer 30) of
this embodiment described above.
OTHER CONFIGURATION EXAMPLES
The specific configuration of the light-modulating cell 10 is not
limited to the above-described example, and the present invention
is also applicable to another light-modulating cell 10 that
includes: a pair of film substrates (a first film substrate 23 and
a second film substrate 24); a pair of transparent electrodes (a
first transparent electrode 25 and a second transparent electrode
26); a pair of alignment films (a first alignment film 27 and a
second alignment film 28); a plurality of spacers 30; and a liquid
crystal layer 29.
FIG. 8 is a view illustrating another example of a cross section of
the light-modulating cell 10. Each of the plurality of spacers 30
in this example has a multilayer structure (two-layer structure in
this example), and is provided so as to penetrate through the
second alignment film 28 and the liquid crystal layer 29.
That is, each of the spacers 30 includes a truncated conical core
portion 40 and a covering portion 41 covering at least a part of
the core portion 40, and penetrates through one of the pair of
alignment films (the second alignment film 28 in this example) and
the liquid crystal layer 29. As illustrated in FIG. 8, the covering
portion 41 of this example covers an upper surface (upper bottom
surface) of the core portion 40 on the first alignment film 27 side
and a side surface (outer surface) of the core portion 40 to be
interposed between the core portion 40 and the first alignment film
27, between the core portion 40 and the liquid crystal layer 29,
and between the core portion 40 and the second alignment film 28.
Incidentally, the covering portion 41 of this example is formed
using the same member as the second alignment film 28 and is formed
integrally with the second alignment film 28. Therefore, the
"covering portion 41 interposed between the core portion 40 and the
second alignment film 28 (see dotted-line portions in FIG. 10)"
substantially forms a part of the second alignment film 28, and
practically, there is no boundary surface between the covering
portion 41 and the second alignment film 28. On the other hand, a
lower surface (lower bottom surface) of the core portion 40 on the
second transparent electrode 26 side is in contact with the second
transparent electrode 26, and the covering portion 41 is not
interposed between the core portion 40 and the second transparent
electrode 26.
Therefore, each of the spacers 30 of this example has a first
support surface 42 that is in two-dimensional contact with the
other alignment film (the first alignment film 27 in this example)
of the pair of alignment films, and a second support surface 43
being in two-dimensional contact with one of the pair of
transparent electrodes (the second transparent electrode 26 in this
example). The first support surface 42 is formed by the covering
portion 41 and forms the above-described first bottom portion 31.
In addition, the second support surface 43 is formed by the core
portion 40 and the covering portion 41 (the covering portion 41
integrally formed with the second alignment film 28), and forms the
above-described second bottom portion 32. Incidentally, the second
support surface 43 (the second bottom portion 32) of the spacer 30
is formed by the core portion 40 and the covering portion 41, and
only a part of the second support surface 43 is formed by the core
portion 40 in this example, but the entire second support surface
43 may be formed by the core portion 40.
The other configurations are the same as those of the
light-modulating cell 10 illustrated in FIG. 2, and the same or
similar configurations as those of the light-modulating cell 10
illustrated in FIG. 2 will be denoted by the same reference signs,
and the detailed description thereof will be omitted.
According to the light-modulating cell 10 of this example, it is
possible to highly accurately and simply form the spacer 30 based
on a photolithography technique to be described later. In
particular, it is possible to form the covering portion 41 (the
first support surface 42) and the first alignment film 27 using the
same member by forming the covering portion 41 of each of the
spacers 30 using the same member as the second alignment film 28
and forming the first alignment film 27 and the second alignment
film 28 using the same member.
In addition, it is possible to provide the spacer 30 excellent in a
position fixing property by providing each of the spacers 30 so as
to penetrate through the second alignment film 28 and the liquid
crystal layer 29. That is, each of the spacers 30 is also supported
by the second alignment film 28 so that it is possible to
effectively prevent each of the spacers 30 from moving due to an
external force or the like. Incidentally, the first alignment film
27 and the second alignment film 28 are illustrated to have the
same thickness as the liquid crystal layer 29 in the drawing, but
the actual first alignment film 27 and second alignment film 28 are
formed to be extremely thin.
In addition, since each of the spacers 30 has the multilayer
structure, it is possible to easily impart various characteristics
to each of the spacers 30. For example, it is possible to realize
the spacer 30 excellent in surface characteristics while securing
high proof stress performance by forming the covering portion 41
with a member having small influence on the liquid crystal layer 29
while forming the core portion 40 of each of the spacers 30 with a
member having excellent rigidity. Incidentally, each of the spacers
30 has the two-layer structure in the above-described example, but
each of the spacers 30 may be configured using three or more
layers.
Even in this example, the periodicity of mutual interference of
diffracted light generated by the respective spacers 30 disappears
by making a distance between the spacers 30 inconstant, and it is
possible to reduce the influence of interference of diffracted
light generated by the plurality of spacers 30 and to provide
observation light excellent in visibility.
<Guest-Host Liquid Crystal>
The present invention is also applicable to a light-modulating cell
10 employing a guest-host liquid crystal. That is, a liquid crystal
layer 29 may contain a dichroic pigment (guest) and a liquid
crystal (host). The dichroic pigment contained in the liquid
crystal layer 29 is preferably a coloring material that has a light
shielding property and capable of shielding (absorbing) desired
visible light.
A specific configuration of the light-modulating cell 10 employing
the guest-host liquid crystal to which the present invention is
applicable is not particularly limited. For example, only one
polarizing plate may be provided as illustrated in FIGS. 9A to 10B
to be described later, or a polarizing plate is not necessarily
provided as illustrated in FIGS. 11 and 12 to be described later,
instead of providing a pair of polarizing plates (see the first
polarizing plate 21 and the second polarizing plate 22 in FIG. 2).
Hereinafter, a typical example of the light-modulating cell 10
employing the guest-host liquid crystal will be described.
FIGS. 9A and 9B are conceptual views for describing an example
(light shielding state) of the light-modulating cell 10 employing
the guest-host liquid crystal, FIG. 9A is a cross-sectional view of
the light-modulating cell 10, and FIG. 9B is a plan view of a first
polarizing plate 21 in which an absorption axis direction is
indicated by an arrow "A". FIGS. 10A and 10B are conceptual views
for describing the same light-modulating cell 10 (a light
transmitting state) as FIGS. 9A and 9B, FIG. 10A is a
cross-sectional view of the light-modulating cell 10, and FIG. 108
is a plan view of the first polarizing plate 21 in which the
absorption axis direction is indicated by an arrow "A".
Incidentally, an absorption axis of the first polarizing plate 21
and a polarization axis (light transmission axis) extend in
directions vertical to each other.
The light-modulating cell 10 of this example has basically the same
configuration as that of the light-modulating cell 10 illustrated
in FIG. 2. That is, the light-modulating cell 10 illustrated in
FIGS. 9A to 10B also includes: a pair of film substrates (a first
film substrate 23 and a second film substrate 24); a pair of
transparent electrodes (a first transparent electrode 25 and a
second transparent electrode 26) arranged between the pair of film
substrates; a pair of alignment films (a first alignment film 27
and a second alignment film 28) arranged between the pair of
transparent electrodes; a plurality of spacers 30 supporting at
least any one of the pair of alignment films and being in
two-dimensional contact with at least any one of the pair of
alignment films; and the liquid crystal layer 29 arranged between
the plurality of spacers 30 between the pair of alignment films,
and in which at least some of the plurality of spacers 30 have an
inconstant distance to the other spacer 30 positioned at the
closest distance, which is similar to the light-modulating cell 10
illustrated in FIG. 2. In the light-modulating cell 10 illustrated
in FIGS. 9A to 10B, however, only one polarizing plate (the first
polarizing plate 21 in this example) is provided on the opposite
side of the pair of transparent electrodes with one of the pair of
film substrates (the first film substrate 23 in this example)
interposed therebetween. In addition, the liquid crystal layer 29
is configured using the guest-host liquid crystal containing
dichroic pigments (dyes) 51 and liquid crystals 52.
The dichroic pigments 51 exist in a dispersed state in the liquid
crystals 52, have the same alignment as the liquid crystals 52, and
are basically aligned in the same direction as the liquid crystals
52.
In this example, when a voltage between the pair of transparent
electrodes (the first transparent electrode 25 and the second
transparent electrode 26) is in an OFF state, the dichroic pigment
51 and the liquid crystal 52 are aligned in the horizontal
direction (particularly, a direction vertical to the absorption
axis direction A of the first polarizing plate 21 (that is, the
same direction as the polarization axis of the first polarizing
plate 21)) vertical to the light traveling direction L (that is,
the stacking direction of the light-modulating cell 10) (see FIG.
9A). On the other hand, when the voltage between the pair of
transparent electrodes (the first transparent electrode 25 and the
second transparent electrode 26) is in an ON state, the dichroic
pigment 51 and the liquid crystal 52 are aligned in the vertical
direction (that is, the light traveling direction L) (see FIG.
10A). Incidentally, FIG. 9A and FIG. 10A conceptually illustrate
the dichroic pigment 51 and the liquid crystal 52 in order to
illustrate the alignment directions of the dichroic pigment 51 and
the liquid crystal 52.
For example, when no voltage is applied to the first transparent
electrode 25 and the second transparent electrode 26 by a
light-modulating controller 12 (see FIG. 1), a desired electric
field is not applied to the liquid crystal layer 29, and the
dichroic pigment 51 and the liquid crystal 52 are aligned in the
horizontal direction (see FIG. 9A). In this case, light vibrating
in the direction orthogonal to the absorption axis direction A of
the first polarizing plate 21 is shielded by the dichroic pigment
51, and light vibrating in the other direction is shielded by the
first polarizing plate 21. Therefore, light traveling in the
direction from the second film substrate 24 toward the first
polarizing plate 21 (see an arrow "L") is shielded by the dichroic
pigment 51 and the first polarizing plate 21.
Incidentally, the spacers 30 of this example are also irregularly
arranged and a distance between the adjacent spacers 30
(particularly, a distance in the direction orthogonal to the light
traveling direction L) is inconstant, which is similar to the
light-modulating cell 10 illustrated in FIG. 2. Thus, the
interference of diffracted light generated by the respective
spacers 30 does not periodically occur, and it is possible to
reduce the influence of interference of diffracted light generated
by the plurality of spacers 30 and provide observation light
excellent in visibility.
On the other hand, when a voltage is applied to the first
transparent electrode 25 and the second transparent electrode 26 by
the light-modulating controller 12 (see FIG. 1), the desired
electric field is applied to the liquid crystal layer 29, and the
dichroic pigment 51 and the liquid crystal 52 are aligned in the
vertical direction (see FIG. 10A). In this case, the light
shielding performance of the dichroic pigment 51 with respect to
the light passing through the liquid crystal layer 29 is hardly
exerted regardless of the light vibrating direction, and the light
entering the liquid crystal layer 29 passes through the liquid
crystal layer 29 (the dichroic pigment 51 and the liquid crystal
52) with a high probability. In addition, the light vibrating in
parallel with the polarization axis (light transmission axis) of
the first polarizing plate 21 (light vibrating in the direction
vertical to the absorption axis direction A of the first polarizing
plate 21 in this example) passes through the first polarizing plate
21 and is emitted from the light-modulating cell 10.
Even in the case of using the guest-host liquid crystal layer 29
illustrated in FIGS. 9A to 10B as described above, it is possible
to appropriately change a light-transmitting property of the
light-modulating cell 10 by controlling the voltage to be applied
to the first transparent electrode 25 and the second transparent
electrode 26.
Incidentally, the other configurations of the light-modulating cell
10 of this example can be made the same as those of the
light-modulating cell 10 illustrated in FIG. 2. For example, each
of the spacers 30 can include a flat first bottom portion 31, which
is made of a photocurable resin and in contact with one (for
example, the first alignment film 27) of the pair of alignment
films, and a second bottom portion 32 opposing the first bottom
portion 31, and have a tapered shape (for example, a taper angle in
a range of 75.degree. or larger and 85.degree. or smaller). In
addition, the plurality of spacers 30 may be configured by
repeatedly arranging unit patterns (see reference sign "50" in FIG.
6) each of which is formed of three or more spacers 30 arranged
with a predetermined relative positional relationship. In addition,
at least any one of the pair of film substrates (the first film
substrate 23 and the second film substrate 24) may be partially or
entirely curved. In addition, each of the plurality of spacers 30
may include a core portion 40 and a covering portion 41 covering at
least a part of the core portion 40, penetrate through one (for
example, the second alignment film 28) of the pair of alignment
films and the liquid crystal layer 29, and have a first support
surface 42 being in two-dimensional contact with the other
alignment film (for example, the first alignment film 27) of the
pair of alignment films and a second support surface 43 being in
two-dimensional contact with one (for example, the second
transparent electrode 26) of the pair of electrodes, and the first
support surface 42 may be formed by the covering portion 41, and at
least a part of the second support surface 43 may be formed by the
core portion 40.
Incidentally, the case of using the so-called normally black type
alignment films 27 and 28 and liquid crystal layer 29 has been
described as above regarding the light-modulating cell 10
illustrated in FIGS. 9A to 10B, but so-called normally white type
alignment films 27 and 28 and liquid crystal layer 29 may be used.
That is, in the case of the normally black type, it is necessary to
cause the dichroic pigment 51 and the liquid crystal 52 to be
aligned in the vertical direction when the electric field is
applied to the liquid crystal layer 29 by applying the voltage
between the electrodes 25 and 26 as described above, and thus, a
horizontal alignment film is used as the alignment films 27 and 28,
and a positive liquid crystal is used for the liquid crystal layer
29. On the other hand, in the case of the normally white type, it
is necessary to cause the dichroic pigment 51 and the liquid
crystal 52 to be aligned in the horizontal direction as illustrated
in FIG. 9A when the electric field is applied to the liquid crystal
layer 29 by applying the voltage between the electrodes 25 and 26,
and thus, a vertical alignment film is used as the alignment films
27 and 28, and a negative liquid crystal is used for the liquid
crystal layer 29. The above-described operational effect that the
influence of the diffracted light generated by the spacer 30 can be
reduced by irregularly arranging the spacer 30 is valid not only in
the light-modulating cell 10 employing the guest-host liquid
crystal of the normally black type but also in the light-modulating
cell 10 employing the guest-host liquid crystal of the normally
white type.
FIG. 11 is a conceptual view for describing another example (a
light shielding state) of a light-modulating cell 10 employing a
guest-host liquid crystal, and illustrates a cross section of the
light-modulating cell 10. FIG. 12 is a conceptual view for
describing the same light-modulating cell 10 (a light transmitting
state) as FIG. 11, and illustrates a cross section of the
light-modulating cell 10.
The light-modulating cell 10 of this example has basically the same
configuration as that of the light-modulating cell 10 illustrated
in FIG. 2, but has a liquid crystal layer 29 of the guest-host type
containing a dichroic pigment (dye) 51 and a liquid crystal 52
without providing a polarizing plate (a first polarizing plate 21
and a second polarizing plate 22). That is, the dichroic pigments
51 exist in a dispersed state in the liquid crystals 52, have the
same alignment as the liquid crystals 52, and are basically aligned
in the same direction as the liquid crystals 52.
In this example, when a voltage between a pair of transparent
electrodes (a first transparent electrode 25 and a second
transparent electrode 26) is in an OFF state, the dichroic pigment
51 and the liquid crystal 52 are aligned in the horizontal
direction (that is, the direction vertical to the light traveling
direction L) (see FIG. 11). In particular, it is preferable that
the alignment of the dichroic pigment 51 and the liquid crystal 52
of this example be twisted by 180 degrees or more with respect to
the horizontal direction in a state where no electric field is
applied so that the dichroic pigments 51 are directed in every
horizontal direction. On the other hand, when the voltage between
the pair of transparent electrodes (the first transparent electrode
25 and the second transparent electrode 26) is in an ON state, the
dichroic pigment 51 and the liquid crystal 52 are aligned in the
vertical direction (that is, the light traveling direction L) (see
FIG. 12). Incidentally, FIGS. 11 and 12 conceptually illustrate the
dichroic pigment 51 and the liquid crystal 52 in order to
illustrate the alignment directions of the dichroic pigment 51 and
the liquid crystal 52.
For example, when no voltage is applied to the first transparent
electrode 25 and the second transparent electrode 26 by a
light-modulating controller 12 (see FIG. 1), a desired electric
field is not applied to the liquid crystal layer 29, and the
dichroic pigment 51 and the liquid crystal 52 are aligned in the
horizontal direction (see FIG. 11). As a result, the light entering
the liquid crystal layer 29 is shielded (absorbed) by the dichroic
pigment 51. Incidentally, the spacers 30 of this example are also
irregularly arranged and a distance between the adjacent spacers 30
(particularly, a distance in the direction orthogonal to the light
traveling direction L) is inconstant, which is similar to the
light-modulating cell 10 illustrated in FIG. 2. Thus, the
interference of diffracted light generated by the respective
spacers 30 does not periodically occur, and it is possible to
reduce the influence of interference of diffracted light generated
by the plurality of spacers 30 and provide observation light
excellent in visibility.
On the other hand, when a voltage is applied to the first
transparent electrode 25 and the second transparent electrode 26 by
the light-modulating controller 12 (see FIG. 1), the desired
electric field is applied to the liquid crystal layer 29, and the
dichroic pigment 51 and the liquid crystal 52 are aligned in the
vertical direction (see FIG. 12). In this case, the light shielding
performance of the dichroic pigment 51 with respect to the light
passing through the liquid crystal layer 29 is hardly exerted
regardless of the light vibrating direction, and the light entering
the liquid crystal layer 29 passes through the liquid crystal layer
29 (the dichroic pigment 51 and the liquid crystal 52) with a high
probability. In addition, since no polarizing plate is provided in
this example, the entire light passing through the liquid crystal
layer 29 and emitted from a first film substrate 23 is emitted from
the light-modulating cell 10.
Even in the case of using the guest-host liquid crystal layer 29
illustrated in FIGS. 11 and 12 as described above, it is possible
to change the light-transmitting property of the light-modulating
cell 10 by controlling the voltage to be applied to the first
transparent electrode 25 and the second transparent electrode
26.
Incidentally, the guest-host light-modulating cell 10 of the
normally black type in which the horizontal alignment film is used
as the alignment films 27 and 28 and the positive liquid crystal is
used for the liquid crystal layer 29 has been described as above
regarding the light-modulating cell 10 illustrated in FIGS. 11 and
12, a guest-host light-modulating cell 10 of a normally white type
may be used. That is, a vertical alignment film is used as the
alignment films 27 and 28, and a negative liquid crystal is used
for the liquid crystal layer 29 such that the dichroic pigment 51
and the liquid crystal 52 may be aligned in the horizontal
direction as illustrated in FIG. 11 when the electric field is
applied to the liquid crystal layer 29 by applying the voltage
between the electrodes 25 and 26. Even in the light-modulating cell
10 employing the guest-host liquid crystal of the normally white
type, the above-described operational effect that it is possible to
reduce the influence of diffracted light generated by the spacers
30 can be achieved by irregularly arranging the spacers 30.
<Method of Manufacturing Light-Modulating Cell 10>
A method of manufacturing the light-modulating cell 10 according to
this embodiment is not particularly limited, and the
light-modulating cell 10 can be manufactured using arbitrary
bonding technique, photolithography technique, or the like. In
particular, the columnar spacer 30 having the tapered shape can be
suitably manufactured by the photolithography technique. In the
case of forming each of the spacers 30 based on the
photolithography technique, irradiation with light with respect to
a resist (exposure step) is performed using a mask in which a
pattern that is defined in accordance with the arrangement of the
respective spacers 30 is formed. Incidentally, a method of forming
the above-described pattern in the mask is not particularly
limited, and, for example, it is possible to randomly arrange all
lattice points (all the spacers 30) by shifting X-Y coordinates of
the respective lattice points (arrangement points of the respective
spacers 30) using an arbitrary method on the basis of a pattern of
a square lattice.
The inventor of the present application has observed a diffraction
state of light with respect to each of a plurality of kinds of
"groups of the spacers 30" having different shift ranges by
changing the shift range of each lattice point of the square
lattice in order to determine the arrangement of the respective
spacers 30. Specifically, as illustrated in FIG. 13, one side of a
square formed by four lattice points (that is, "diagonal lattice
points L2 (diagonal spacers 30)), arranged on diagonal lines having
each lattice point (that is, a "lattice point L1 of interest (the
spacer 30 of interest)") as the center in the square lattice, is
set as a "diagonal pitch P". A limit R of the shift range with
respect to the X-Y coordinates of the lattice point L1 of interest
(the spacer 30 of interest) was restricted to a size of 10% to 50%
of the diagonal pitch P, and the arrangement of the lattice points
L1 of interest (the spacers 30 of interest) was randomly shifted by
using random numbers. Here, the "spacer 30 of interest" does not
indicate only the specific spacer 30 among all the spacers 30, but
each of all the spacers 30 is treated as the "spacer 30 of
interest" referred to herein. That is, the arrangement of all the
spacers 30 is randomly shifted by determining the arrangement of
the respective spacers 30 as described above based on positions of
the diagonal lattice points L2 (diagonal spacers 30) allocated to
each of the spacers 30. As the arrangement of all the spacers 30 is
shifted using the "method of shifting the arrangement of the
spacers 30 of interest based on the positions of the diagonal
lattice points L2" in this manner, it is possible to randomly
arrange all the spacers 30. As a result, a good result that a
diffraction phenomenon was almost inconspicuous was obtained in a
"range where a length of one side of the limit R of the shift range
with respect to the X-Y coordinates of the respective spacers 30 is
30% or more and 50% or less of the diagonal pitch P" although the
diffraction phenomenon was somewhat conspicuous in a "range where
the length of one side of the limit R of the shift range with
respect to the X-Y coordinates of the respective spacers 30 is 10%
or more and less than 30% of the diagonal pitch P".
For example, a process of coating the top of the second transparent
electrode 26 with a photosensitive resin (photocurable resin)
forming the spacer 30, forming the tapered spacer 30 using the
photosensitive resin by the photolithography technique, and then,
forming the second alignment film 28 on the second transparent
electrode 26, and imparting an alignment regulating force to the
second alignment film 28 by rubbing or the like may be performed.
In this case, the alignment imparting process is performed with
respect to the second alignment film 28 in the state where the
spacer 30 has been formed. Incidentally, when the alignment
imparting process for the second alignment film 28 is performed in
a state where the "inverted tapered spacer 30" in which the bottom
portion (first bottom portion 31) of each of the spacers 30 on the
first alignment film 27 side is larger than the bottom portion
(second bottom portion 32) on the second alignment film 28 side is
formed, it is sometimes difficult to impart the sufficient
alignment with respect to the second alignment film 28 in the
vicinity of the spacer 30. Therefore, the "forward tapered spacer
30" in which the bottom portion (first bottom portion 31) of each
of the spacers 30 on the first alignment film 27 side is smaller
than the bottom portion (second bottom portion 32) on the second
alignment film 28 side is preferable from the viewpoint of
imparting the alignment with respect to the second alignment film
28.
Next, a specific example will be described.
Specific Example 1 (Comparative Example)
A light-modulating cell 10 of this example is the light-modulating
cell 10 that controls transmitted light using a liquid crystal. A
liquid crystal layer 29 was sandwiched between films for liquid
crystal orientation layers (a first alignment film 27 and a second
alignment film 28) to prepare a liquid crystal cell, and the liquid
crystal cell was sandwiched between linearly polarizing plates (a
first polarizing plate 21 and a second polarizing plate 22)
arranged in a parallel nicol state, thereby producing the
light-modulating cell 10 of this example. Specifically, the
light-modulating cell 10 of this example has the same layer
structure as the light-modulating cell 10 illustrated in FIG. 2
(that is, the first polarizing plate 21, the second polarizing
plate 22, a first film substrate 23, a second film substrate 24, a
first transparent electrode 25, a second transparent electrode 26,
the first alignment film 27, the second alignment film 28, the
liquid crystal layer 29, and spacers 30 (particularly, spacers
30a)).
A TN liquid crystal is used for the liquid crystal layer 29 in this
example, and a polarization plane of passing light is rotated by
90.degree. in a state where no electric field is applied. The
spacer 30, configured to hold a constant thickness of the liquid
crystal layer 29 (liquid crystal material), is provided between the
films for liquid crystal orientation layers (particularly, the
first alignment film 27 and the second alignment film 28 (strictly
speaking, the second transparent electrode 26)). The spacer 30 of
this example is made of a transparent material and does not have a
light shielding property with respect to visible light. Each of the
spacers 30 was arranged so as to have a constant distance to the
other spacer 30 positioned at the closest distance. In addition, a
film-shaped resin substrate (particularly, a film substrate made of
polycarbonate in this example) was used as the first film substrate
23 supporting the first transparent electrode 25 and the second
film substrate 24 supporting the second transparent electrode 26.
The films for liquid crystal orientation layers were formed by
sequentially producing electrodes (the first transparent electrode
25 and the second transparent electrode 26) and alignment layers
(the first alignment film 27 and the second alignment film 28) with
respect to the film member (substrate).
When light (light from a point light source) having passed through
the light-modulating cell 10 of this example was visually
confirmed, the light from the point light source was affected by
interference of diffracted light generated by the respective
spacers 30, and a light interference region was generated around
the point light source.
Specific Example 2 (Example)
Each of spacers 30 (all spacers 30) used in a light-modulating cell
10 of this example was arranged so as to have an inconstant
distance to the other spacer 30 positioned at the closest distance.
The other configurations of the light-modulating cell 10 of this
example are the same as those of the above-described Specific
Example 1 (comparative example).
When light (light from a point light source) having passed through
the light-modulating cell 10 of this example was visually
confirmed, the influence (light intensity) of interference of
diffracted light generated by the respective spacers 30 on the
light from the point light source was reduced to extent that is
hardly visually recognized by randomly arranging the spacers 30,
and no light interference region was generated around the point
light source.
As described above, it is possible to reduce the influence of
interference of diffracted light generated by the plurality of
spacers 30 and to provide the observation light excellent in
visibility by setting at least some of the plurality of spacers 30
to have an inconstant distance to the other spacer 30 positioned at
the closest distance.
Embodiments of the present invention are not limited to the
individual embodiments described above, but include various
modifications that can be conceived by those skilled in the art,
and the effects of the present invention are not limited to the
above-described content. That is, various additions, modifications,
and partial deletions can be made in a scope not departing from the
conceptual idea and gist of the present invention derived from the
content defined in the claims and their equivalents.
REFERENCE SIGNS LIST
5 Light-modulating system 10 Light-modulating cell 12
Light-modulating controller 14 Sensor device 16 User operation unit
21 First polarizing plate 22 Second polarizing plate 23 First film
substrate 24 Second film substrate 25 First transparent electrode
26 Second transparent electrode 27 First alignment film 28 Second
alignment film 29 Liquid crystal layer 30 Spacer 31 First bottom
portion 32 Second bottom portion 34 Unit pattern 35 Unstable area
40 Core portion 41 Covering portion 42 First support surface 43
Second support surface 50 Unit pattern area 51 dichroic pigment 52
Liquid crystal
* * * * *